The present invention relates to voltage surge protection devices and, more particularly, to means and methods for mounting an overvoltage protection module.
Frequently, excessive voltage is applied across service lines that deliver power to residences and commercial and institutional facilities. Such excess voltage or voltage spikes may result from lightning strikes, for example. The voltage surges are of particular concern in telecommunications distribution centers, hospitals and other facilities where equipment damage caused by voltage surges and resulting down time may be very costly.
Typically, one or more varistors (i.e., voltage dependent resistors) are used to protect a facility from voltage surges. Generally, the varistor is connected directly across an AC input and in parallel with the protected circuit. The varistor has a characteristic clamping voltage such that, responsive to a voltage increase beyond a prescribed voltage, the varistor forms a low resistance shunt path for the overvoltage current that reduces the potential for damage to the sensitive components. Typically, a line fuse may be provided in the protective circuit and this line fuse may be blown or weakened by the essentially short circuit created by the shunt path.
Varistors have been constructed according to several designs for different applications. For heavy-duty applications (e.g., surge current capability in the range of from about 60 to 100 kA) such as protection of telecommunications facilities, block varistors are commonly employed. A block varistor typically includes a disk-shaped varistor element potted in a plastic housing. The varistor disk may be formed by pressure casting a metal oxide material, such as zinc oxide, or other suitable material such as silicon carbide. Copper, or other electrically conductive material, may be flame sprayed onto the opposed surfaces of the disk. Ring-shaped electrodes are bonded to the coated opposed surfaces and the disk and electrode assembly is enclosed within the plastic housing. Examples of such block varistors include Product No. SIOV-B860K250 available from Siemens Matsushita Components GmbH and Co. KG and Product No. V271BA60 available from Harris Corporation.
Another varistor design includes a high-energy varistor disk housed in a disk diode case. The diode case has opposed electrode plates and the varistor disk is positioned therebetween. One or both of the electrodes include a spring member disposed between the electrode plate and the varistor disk to hold the varistor disk in place. The spring member or members provide only a relatively small area of contact with the varistor disk.
The varistor constructions described above often perform inadequately in service. Often, the varistors overheat and catch fire. Overheating may cause the electrodes to separate from the varistor disk, causing arcing and further fire hazard. There may be a tendency for pinholing of the varistor disk to occur, in turn causing the varistor to perform outside of its specified range. During high current impulses, varistor disks of the prior art may crack due to piezoelectric effect, thereby degrading performance. Failure of such varistors has led to new governmental regulations for minimum performance specifications. Manufacturers of varistors have found these new regulations difficult to meet.
U.S. Pat. No. 6,038,119 to Atkins et al., the disclosure of which is hereby incorporated herein by reference in its entirety, discloses overvoltage protection modules including wafers of varistor material. The overvoltage protection modules described therein may address the problems described above.
Overvoltage protection devices, circuit breakers, fuses, ground connections and the like are often mounted on DIN (Deutsches Institut fxc3xcr Normung e.V.) rails. DIN rails may serve as mounting brackets of standardized dimensions so that such electrical control devices may be sized and configured to be readily and securely mounted to a support surface such as an electrical service utility box.
According to embodiments of the present invention, an overvoltage protection assembly includes a rail and a mount device. The mount device includes a base member having front and rear opposed surfaces and a mounting structure on the rear surface. The mounting structure secures the base member to the rail. An overvoltage protection module is mounted on the front surface of the base member.
According to further embodiments of the present invention, an overvoltage protection assembly for mounting on a rail includes a mount device. The mount device includes a base member having front and rear opposed surfaces and a mounting structure on the rear surface. The mounting structure is adapted to secure the base member to the rail. An overvoltage protection module is mounted on the front surface of the base member.
According to further embodiments of the present invention, a mount device for mounting an overvoltage protection module on a rail includes a base member having front and rear opposed surfaces and a mounting structure on the rear surface. The mounting structure is adapted to secure the base member to the rail. The base member is adapted to securely engage the overvoltage protection module. The base member is formed of metal.
According to further embodiments of the present invention, a mount assembly for mounting an overvoltage protection module on a support includes a rail and a mount device. The mount device includes a base member having front and rear opposed surfaces and a mounting structure on the rear surface. The mounting structure secures the base member to the rail. The base member is adapted to securely engage the overvoltage protection module. The base member is formed of metal.
According to method embodiments of the present invention, a method of mounting an overvoltage protection module on a rail includes providing a mount device including a base member having front and rear opposed surfaces and a mounting structure on the rear surface. The base member is secured to the rail using the mounting structure. An overvoltage protection module is mounted on the front surface of the base member.
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention.